package com.wenhao.newfeature;

import com.sun.org.apache.xerces.internal.impl.xpath.XPath;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class MapDemo {
    public static void main(String[] args) {
        Map<String,String> map = new HashMap<>();
        Map<String,String> temp = new HashMap<>();
        // 不能传null
        map.putAll(temp);
        Map<String,String> currentMap = new ConcurrentHashMap<>();
        currentMap.put("1","2");
    }
}
